Load sensing system

ABSTRACT

A processor implemented stabilization system for load handling equipment monitors at least a portion of the equipment weight load at an equipment support member. Reduction below or increase above predetermined values signals an approaching tip over condition and triggers alarm condition responses for stabilization of the equipment. In a counterbalanced lift truck, the equipment weight load on a rear steer wheel is carried by an outer bearing race of a spindle and is transferred from the race to a load cell which is positioned between the race and a shoulder of a mounting tube. The load cell output is received at a processor which monitors the cell to determine if there is an approaching longitudinal tip over condition (toward or away from the load) as well as a lateral tip over condition. Upon sensing an approaching tip over condition, the processor implements one or more corrective measures such as actuation of an annunciator, preventing an increase in vehicle speed, preventing elevation of the load, preventing mast tilt, etc.

RELATED APPLICATION

This application is a division of application Ser. No. 08/821,963 filedMay 30, 1997 and issued Apr. 18, 2000 as U.S Pat. No. 6,050,770.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention deals with load handling equipment and more particularlywith a system for sensing an approaching tip over condition.

2. Antecedents of the Invention

Of paramount significance in the design of load handling equipment weresafety considerations including equipment stability over a range ofoperating conditions, both loaded and unloaded.

Although each piece of load handling equipment was rated for a maximumwork load, the fact that the equipment load was within the rated weightload range did not constitute a guarantee of stability. This was becausenumerous additional parameters affected stability of the equipment. Forexample, if a load within the maximum load weight range was loaded offcenter, i.e. with a center of gravity displaced forwardly of a loadmoment axis, beyond a rated distance, or if the load center of gravitywas displaced laterally from the longitudinal equipment axis, such aswhen a side shifter was employed, a determination that the load weightwas within the specified range did not alone assure that safe equipmentoperation without tip over resulted. In lift trucks, additional factorssuch as mast tilt angle, mast load elevation, vehicle support surfaceslope, i.e. ramp incline, vehicle acceleration or deceleration,centrifugal force, etc. all constituted significant additional factorsaffecting stability.

Although systems have been devised for determining load weight, such asthat disclosed in U.S. Pat. No. 5,105,896, knowledge of the load weightalone was insufficient. In U.S. Pat. No. 3,841,493, the load moment in acrane having an elongate boom was monitored by sensing the hydraulicpressure differential in a hydraulic cylinder employed to support theboom. Knowledge of the load moment alone was not sufficient to assureequipment stability, however, due to the many other variable factorswhich affected the dynamic interaction between load moment and equipmentcounterbalance moment.

It has also been proposed to detect an overload condition of a fork liftvehicle by utilizing a strain guage in a mounting bracket of a tiltcylinder, as disclosed in U.S. Pat. No. 3,993,166. The disclosed systemwas imprecise and did not provide an assessment of vehicle stability.

U.S. Pat. No. 5,224,815 described a load state monitoring system for alift truck. The system employed strain gages to sense both horizontaland vertical mast bearing forces on a horizontally spaced pair of pivotbearings. The sum of sensed vertical forces was to correspond to thestatic load supported by the mast and the sum of the sensed horizontalforces was to correspond to the load moment.

As with the load moment monitoring system of U.S. Pat. No. 3,841,493,detection of the load moment alone was not determinative of equipmentstability. Knowledge of the effect of the counterbalance moment wasessential in an assessment of stability.

The prior systems did not sense the effects of the instantaneousequipment counterbalance moment which was a function of many variables,such as the weight of the lift truck operator, the employment ofauxiliary extension weights on the back of the equipment to increase theload capacity, the angle of incline of the support surface, theelevation of the load, the mast tilt angle, vehicle deceleration oracceleration, centrifugal force, the employment of mast accessories,etc.

Essentially, the previous systems which attempted to guage equipmentstability merely employed a deduction process for approximatingstability since no assessment was made with respect to the instantaneouscounterbalance moment and its effect on stability.

Further, a true stabilization sensing system must recognize when theoverall center of gravity is about to be transferred to a point outsideof a polygon defined by the contact points between support members, e.g.wheels, and a support surface.

Prior systems were unable to recognize a reverse tip over condition,that is, a longitudinal axis tip over in the counterbalance momentdirection, which could occur with an elevated load and equipmenttraversing an upwardly sloped ramp, with or without the mast beingLilted rearwardly.

Additionally, stabilization systems must also sense and respond to anapproaching lateral tip over condition, as a result of centrifugalforce, lateral ramp slope or a laterally offset load center of gravity.

Safety standards for lift trucks have been adopted by the AmericanNational Standards Institute (ANSI). The standards are entitled “SafetyStandard for Low Lift and High Lift Trucks, ASME B56.1-1993 copyright1994, The American Society of Mechanical Engineers.

Part III of ANSI B56.1, entitled “Design and Construction Standards”,Section 7.6 et seg. sets forth the stability criteria for lift trucksand standards for measurement of a truck's resistance to overturningunder controlled static conditions which include consideration fordynamic factors encountered during equipment operation. The testingcriteria recognized factors which influenced stability including loadweight, weight distribution, wheel base, wheel tread, method ofsuspension, truck speed, as well as tire and mast deflection under load.

Different stability tests have been established for counterbalanced lifttrucks (Section 7.7), narrow aisle high lift trucks (Section 7.8), highlift order picker trucks (Section 7.9), counterbalanced front/sideloader lift trucks (Section 7.10) and single sided loader lift trucks(Section 7.11).

All of the tests involved placing the equipment on a tilting platformwhich comprised a rigid flat surface and tilting the platform to theslope specified for each of the required tests. The truck was consideredstable if it did not physically overturn when the test platform wastilted to the specified slope values.

For counterbalanced lift trucks, the platform tests for longitudinalstability included a stacking test, with the mast raised and forkscarrying a test load, as well as a test simulating travellingconditions, with the test load being lowered and the mast rearwardlytilted. Lateral stability tests for counterbalanced lift trucks includeda stacking test with a test load carried in the mast uppermost positionand rearwardly tilted as well as a travelling test without a load.

It was evident that prior systems for detecting a potential tip overcondition, which assessed stability as a function of either the loadweight or the load tip over moment, merely served to deduce a possibleapproaching equipment tip over state, since the variable factorsaffecting the counterbalance moment and other equipment stabilityconsiderations were not taken into account.

SUMMARY OF THE INVENTION

In compendium, the invention comprises a stabilization system for loadhandling equipment. The system senses a normal component vector ofequipment weight carried by a support member. The support member isspaced longitudinally from a transverse pivot axis of a load tip overmoment, e.g. a mast pivot axis. The sensed equipment weight componentcarried by the support member decreases as a function of increasing tipover moment and counterbalance moment and represents a measure ofequipment stability.

When the support member, such as a rear steer wheel, bears no loadcomponent, any increase in the tip over moment will no longer generatean increase in the counterbalance moment and will cause the supportmember to lift from the support surface. Further increase in tip overmoment will cause the equipment to tip over.

Conversely, an increase in the sensed equipment weight load componentbeyond a maximum value signals reverse instability caused by a transferof the load center of gravity toward and beyond the moment axis.

The normal component vector of equipment weight at the support member issensed by a transducer such as a load cell. The load cell may comprisean annulus positioned within a steer wheel vertical spindle support. Theaxial load on the spindle is transferred through a bearing race to theload cell which is between the race and a thrust shoulder within thespindle support.

A processor monitors the transducer. If an approaching tip overcondition is sensed, the processor automatically implements correctivesteps including operator alarm annunciator actuation, selectivedisablement of load elevation function, selective disablement of masttilt function, and disablement of auxiliary functions such as a sideshifters.

From all of the foregoing, it will be appreciated that it is aconsideration of the present invention to provide a stabilization systemof the general character described for load handling equipment which isnot subject to the disadvantages of the antecedents of the invention.

A feature of the present invention is to provide a stabilization systemof the general character described for load handling equipment whichprovides an assessment of equipment stability by monitoring the statusof an equipment weight component at a support, rather than monitoringthe load moment of the equipment.

An aspect of the present invention is to provide a stabilization systemof the general character described for load handling equipment whichprovides a true measure of stability regardless of variations in avariety of stability factors including the longitudinal slope or inclineof a support surface.

A further consideration of the present invention is to provide astabilization system of the general character described for loadhandling equipment which is responsive to instability factorsattributable to the lateral slope or incline of the equipment supportsurface.

An additional feature of the present invention is to provide astabilization system of the general character described for loadhandling equipment which provides an assessment of instantaneous vehiclestability irrespective of load position.

Another aspect of the present invention is to provide a stabilizationsystem of the general character described for load handling equipmentwhich provides an indication of instantaneous equipment stability of alift truck and which is responsive to instability factors attributableto vehicle acceleration and deceleration.

An additional consideration of the present invention is to provide astabilization system of the general character described for loadhandling equipment which includes a transducer for generating a signalrepresentative of a component of equipment weight load at a vehiclesupport, with the weight load varying as a function of equipmentstability.

Yet another aspect of the present invention is to provide astabilization system of the general character described for loadhandling equipment which is responsive to changes in the equipmentcounterbalance moment.

A still further feature of the present invention is to provide astabilization system of the general character described for loadhandling equipment which is responsive to lateral instability factorsattributable to centrifugal force.

To provide a stabilization system of the general character described forload handling equipment which is responsive to lateral instabilityfactors attributable to a load center of gravity being displaced fromthe longitudinal equipment axis is another aspect of the presentinvention.

A still further consideration of the present invention is to provide amethod of monitoring load handling equipment stability which overcomesthe disadvantages aforementioned.

Yet another feature of the present invention is to provide a method ofmonitoring load handling equipment stability by monitoring at least acomponent of the equipment weight load at an equipment support.

Other aspects, features and considerations of the present invention inpart will be obvious and in part will be pointed out hereinafter.

With these ends in view, the invention finds embodiment in certaincombinations of elements, arrangements of parts and series of steps bywhich the aforesaid aspects, features and considerations and certainother aspects, features and considerations will be attained, all withreference to the accompanying drawings and the scope of which will bemore particularly pointed out and indicated in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings in which are shown one of the variouspossible exemplary embodiments of the invention,

FIG. 1 is a front elevational view of a counterbalanced lift truckcarrying a load on a fully elevated mast assembly, with the lift truckhaving a stabilization system constructed in accordance with andembodying the invention;

FIG. 2 is a schematized top plan footprint of the truck illustrated inFIG. 1 showing a rear steer wheel and a pair of front drive wheels andshowing wheel contact with a support surface, a load center of gravityand the truck center of gravity;

FIG. 3 is a partially exploded isometric view of the lift truck, withportions deleted for clarity and further portions broken away andillustrating a rear steer wheel having a spindle with an axis normal tothe support surface, a support tube which carries the spindle and atransducer for monitoring the axial, i.e. normal load on the steerwheel;

FIG. 4 is an enlarged scale transverse sectional view through thespindle, the support tube, the transducer and related structure of thelift truck;

FIG. 5 is an enlarged scale fragmentary sectional view through thespindle and tube assembly and more clearly illustrating a tapered rollerbearing, a pair of bearing races and the transducer;

FIG. 6 is a schematized top plan footprint of an alternate lift truckhaving a pair of rear steer wheels and a pair of front drive wheels;

FIG. 7 is a schematized block diagram of a processor implementation ofthe stabilization system;

FIG. 8 is a schematized flow chart showing a typical processor routinefor stabilization monitoring and implementation of corrective measuresupon detection of an approaching tip over condition; and

FIG. 9 is a schematized block diagram of an alternate limplementation ofthe stabilization system.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now in detail to the drawings, the reference numeral 10denotes generally a counterbalanced lift truck including a stabilizationsystem constructed in accordance with and embodying the invention. Thecounterbalanced lift truck 10 includes a truck body 12 having a stand upoperator station 14. The lift truck 10 is depicted as an electric truck.Accordingly, the body 12 also includes a battery compartment 16.

A mast such as a triplex mast assembly 18 is mounted to a front end ofthe truck 10. Fixed to a pair of inner rails of the mast assembly 18 isa load engaging carriage 20 having a pair of forks 22 which carry a load24, depicted schematically in FIG. 1. The carriage may also include aside shifting mechanism or other accessories such as a rotator, apush/pull, a carton clamp, a bale clamp, etc.

The load is illustrated, in exemplary manner, as having a load center ofgravity 26. A pair of tilt cylinders 28 interconnect the truck body 12and the mast assembly 18 to tilt the mast assembly for the purpose ofengaging and maneuvering loads.

The lift truck 10 includes a pair of forward drive wheels, i.e. a rightdrive wheel 30 and a left drive wheel 32, illustrated in FIG. 2. Thedrive wheels 30, 32 rotate about a common transverse axis 33 which maybe coincident with the tilt axis of the mast assembly 18. Each drivewheel is engaged by a traction motor (not shown).

The truck 10, with its load 24, is supported above a support surface 36by the right and left drive wheels 30, 32 as well as a rear steer wheel34.

With reference now to FIG. 2, wherein a top plan view footprint showingthe drive wheels 30, 32 and the steer wheel 34 is found, it should benoted that as a counterbalanced lift truck, all of the load 24, duringnormal transporting, is external to a polygon, e.g. a triangle 38,formed by the contact points between the wheels and the support surface36. The triangle 38 also constitutes a stability polygon within whichthe overall center of gravity, i.e. the combined center of gravity ofboth the truck 10 and the load 24, must lie for the truck to remainstable.

With reference to the ANSI B56.1 standards for stability of lift trucks,incorporated herein by reference, the stability standards for lifttrucks are based upon actual vehicle tip over, that is, the lift trucklifting from the tilt platform at one or more points and overturning.

Naturally, during normal operating conditions the tip over moment,created by the load weight multiplied by the load weight moment arm,i.e. the distance from the actual load center of gravity 26 to the drivewheel axis 33, plays a significant role in equipment stability, however,vehicle stability is dependent upon several additional factors.

With reference to FIG. 2, the load weights at each of the vehicle wheels30, 32, 34 have been measured. The following values have been recordedwith respect to a Schaeff W40 triplex mast electric counterbalanced lifttruck, available from Schaeff Incorporated, Sioux City, Iowa, theassignee of the present invention.

With the counterbalanced lift truck having a battery weighing 2900pounds and a total unloaded weight of 9931 pounds, a wheel base of51.250 inches, a transverse center to center drive wheel spacing of 35inches, the unloaded or empty truck center of gravity 40 was spaced adistance of 23.336 inches from the drive wheel axis 33 as denoted by thedouble arrow 42 and spaced from the longitudinal axis of the lift trucka distance of 1.961 inches.

The unloaded truck weight distribution was measured at 3210 pounds atthe right drive wheel 30, 2185 pounds at the left drive wheel 32 and4536 pounds at the steer wheel.

When a load 24 of 3845 pounds was carried on the forks, the measuredweight load on the right drive wheel 30 increased to 5864 pounds; themeasured weight load on the left drive wheel 32 increased to 6142 poundsand the measured load on the steer wheel decreased by 2766 pounds to1770 pounds.

The overall center of gravity 40 a of the loaded truck shifted from theoriginal position toward the axis 33 to a new position which was spacedfrom the axis 33 a distance of 6.581 inches and spaced from thelongitudinal axis of the truck 1.414 inches.

Determination of the position of the static overall center of gravity 40a may be made by adding all of the weight components, e.g. truck weight,mast weight, load weight, fork weight, etc. to obtain a total weightvalue, adding all of the moments, e.g. load weight tip over moment,truck weight moment, etc. and dividing the total weight value by the sumof the moment values.

It is evident that as the weight of the load 24 increases or otherparameters affecting tip over moment, e.g. forward mast tilt angle,vehicle deceleration, etc. increase, the tip over moment increases andthe weight load at the steer wheel 34 will decrease further to a pointwherein the steer wheel 34 bears no load. Further increase in the tipover moment will result in the steer wheel 34 lifting from the supportsurface 36 and additional increases in tip over moment thereafter willresult in the truck 10 tipping over about the axis 33.

Since the tip over moment includes numerous factors in addition to theload weight and load center of gravity, in accordance with theinvention, the value of the tip over moment is not utilized to sense anapproaching tip over condition rather, the component vector of weightload which is normal to the support surface 36 at one or more vehiclesupport wheels is monitored to sense that the truck is about to liftfrom the support surface, which event constitutes an approaching tipover condition.

While the following description refers to monitoring a rear steer wheelof a counterbalanced lift truck, any other equipment support member maybe selected in connection with load handling equipment may be selectedas the site for monitoring equipment weight for the purpose of sensingan approaching tip over condition. In this regard, the load weight onone or more support legs of a crane, for example, may be monitored tosense an approaching tip over condition. Additionally, with reference toFIG. 6 wherein a truck having a pair of drive wheels 30, 32 and a pairof steer wheels 34, 35 is illustrated, the weight load component of bothsteer wheels 34, 35 may be simultaneously monitored, by monitoring ofsuspension components, which bear the weight load. The rear steer wheels34, 35 articulate about a common pivot point 37 such that the vehiclestability polygon comprises a triangle 39 similar to the triangle 38.

With reference now to FIG. 3, it will be seen that the rear steer wheel34 of the truck 10 rotates about a horizontal axle 42 which extendsthrough registered apertures formed in opposed legs of a yoke 44.Steering of the lift truck 10 is effected by rotating the yoke 44 abouta vertical axis 46. For this purpose, a vertical spindle 48 is fixed toa horizontal top of the yoke 44 by a suitable weld 50.

The spindle 48 is received within a support tube 52. The support tube 52is secured within a solid counterweight steer support chassis 54. At itslower end, the chassis 54 is bonded by a weld 55 to a base plate 56 ofthe truck and includes an open downwardly facing well 58 which receivesthe yoke 44 and the steer wheel 32, leaving a lower portion of the steerwheel 32 projecting beneath the base plate 56 to contact the supportsurface 36.

The support tube 52 includes, at its lower end, a pair of radiallyprojecting limit stops 60 which are engaged by a pin 62 (shown in FIG.3) projecting from the yoke 44 to limit rotation of the steer wheelabout the axis 46. The support tube 52 is received within a cylindricalbore 64 which extends through the chassis 54 and is secured to thechassis 54, at opposite ends of the bore 64, by suitable welds 66.

With reference now to FIG. 5, wherein the lower ends of the spindle 48and the support tube 52 are shown in greater detail, it is noted that alower cylindrical base portion 68 of the spindle 48 is of an enlargeddiameter and includes an upper shoulder 70. From the shoulder 70, anintermediate cylindrical portion 72 of the spindle 48 extends upwardlyat a reduced diameter.

The corresponding portions of the support tube 52 comprise a firstshoulder 74, which serves as a limit stop for a seal 76 and an interiorcylindrical bore 75 which extends upwardly to a thrust load bearingshoulder 78. The bore 75, between the shoulders 74, 78, is of uniformdiameter. Seated on the spindle shoulder 70 is an inner race 80 of atapered roller bearing assembly 82. An outer race 84 of the bearing 82engages the cylindrical bore 75 of the support tube 52.

Pursuant to the invention, the outer race 84 is not force fit into thebore 75. The fit is only tight enough to prevent rotation of the outerrace 84, while permitting the axial thrust load on the spindle 48 to betransferred to the top axial end of the race 84.

In accordance with the invention, positioned between the top axial endof the race 84 and the support tube shoulder 78 is an annular weightload transducer 86 which may comprise a load cell.

It is evident that the load cell 86 is subject to the axial component ofthe weight load carried by the spindle 48, hence the steer wheel 34.Suitable electrical leads 88 extend through the support tube 52 from thetransducer 86 to an opening 90 adjacent an upper end of the tube. Anelectrical connector 92 is provided at the end of the leads 88 forinterconnection with appropriate electrical circuitry as will be shownhereinafter.

Mounted across the upper end of the support tube 52 is a solid plate 94having a reduced diameter bore. A tapered roller bearing assembly 96 ispositioned between the bore of the plate 94 and the spindle 48.

A steer motor bracket 98 is bolted to the top of the plate 94 and aspindle pinion 100 having internal teeth is engaged over external teeth102 formed adjacent the upper end of the spindle 48. A bolt 101 isengaged over a terminal portion of the spindle 48 to retain the pinion100.

A steer motor 104 is mounted to the bracket 98 and a drive gear 106,fixed to the end of a steer motor output shaft, engages external teethof the pinion 100 to rotate the spindle 48, hence the yoke 44 and thesteer wheel 32 for steering the lift truck 10.

A steer position sensor 108 engages the top of the spindle 48 to providea signal indicative of the steer wheel position.

With reference again to FIGS. 1 and 2, it will be appreciated that thetransducer 86 generates a signal indicative of the axial weight load,i.e. the weight component normal to the plane of the support surface 36.Such signal constitutes a true representative measure of theinstantaneous stability of the lift truck 10.

Reduction of the spindle axial load below a predetermined valueindicates approaching vehicle instability, regardless of the tip overmoment component attributable to the load 24. By sensing when thevehicle is about to be lifted from the support surface, the presentinvention accounts for all variable parameters which affect stability.

Referring now to FIG. 7 wherein a schematized system block diagramshowing implementation of the stabilization system in a processorcontrolled lift truck, a processor 110 is employed to control theoverall operation of the truck 10, including the drive motors, as wellas hydraulic systems such as mast elevation and tilt controls and mastaccessories. The transducer 86, e.g. load cell, varies in electricalresistance as a function of the axial component of the equipment weightload and is employed in a conventional Wheatstone bridge circuit 112,which may comprise a linear bridge circuit using an operationalamplifier. The bridge output is received at an analog to digitalconverter 114 and the digital output of the converter 114 is received atthe processor 110.

Upon sensing an approaching tip over condition, the processor 110 willactuate a suitable tip over annunciator 116 which may comprise anaudible as well as visual annunciator. Additionally, the processor 110selectively disables certain of the hydraulic fluid controls 118 topermit operator control of the fluid controlled functions only in adirection which would tend to stabilize the vehicle.

In addition to selective disablement of fluidic controls, the processor,upon sensing an approaching tip over condition, effects stabilizinglimitations upon operator throttle selection of the drive motor speedcontrol 120.

A flow chart depicting various processor implemented steps of a typicalroutine for the stabilization system, is depicted in FIG. 8.

Upon entering the routine, the processor first inquires as to whetherthe monitored axial weight component is below the minimum predeterminedvalue as indicated in an inquiry box 122. If the monitored weightcomponent is below the minimum value which is indicative of anapproaching forward tip over condition, the processor then proceeds toeffect control over the hydraulic fluid control system 118 to lock themast against forward tilting as indicated in block 124, since furtherforward tilting tends to increase the tip over moment.

If, on the other hand, the monitored weight is not below the minimumvalue, the processor then inquires as to whether or not the weight isabove the maximum value, which would indicate an approaching reverse tipover condition, as indicated in inquiry box 126. If the monitored weightcomponent is not above the maximum value, the processor exits theroutine. If the monitored weight component value is above the maximum,the processor then effects control of the hydraulic system to lock themast against rearward tilt as indicated in box 128 because furtherrearward tilting of the mast would increase reverse instability.

After effecting the mast tilt locking function of either block 124 orblock 128, the processor then proceeds to lock the mast against furtherelevation as indicated in block 130, since elevation of the loadincreases instability.

Thereafter, the processor 110 proceeds to lock out auxiliary functionsassociated with the mast such as side shifters as indicated in block132. The processor then effects control over the speed of the drivemotors to prevent the operator from increasing the vehicle speed asindicated in block 134. Finally, the processor actuates the operatorannunciator 116 comprising audio and/or visual alarm as indicated inblock 136 to warn the operator of the approaching condition and allowthe operator to effect permitted control operations, e.g. lowering ofmast, tilting of mast in permitted direction, maintaining or reducingtravel speed, increasing turn radius, etc. to bring the stability withinpermitted limits. After actuating the annunciator functions as indicatedin block 136, the processor exits the routine. The processor 110reenters the routine to reassess the stability of the vehicle atpredetermined time intervals.

It should be appreciated that the order of steps in the routine afterthe initial inquiry boxes is not critical and may be altered, rearrangedor revised. Among the primary aspects of the invention is to providesuitable annunciator actuation to warn the operator to take appropriatecorrective measures. In the processor implementation routine illustratedin FIG. 8, additional safeguards have been added to prevent the operatorfrom effecting vehicle control functions which would increaseinstability.

It should also be appreciated that the stabilization system of thepresent invention should not be construed as being limited to processorimplemented equipment control systems. For example, illustrated in FIG.9 is a circuit for actuation of the annunciator 116. The stabilizationsystem depicted therein comprises a transducer 86 coupled to aWheatstone bridge 112. The output of the bridge 112 is received at aninput of a pair of comparators, a minimum load comparator 138 and amaximum load comparator 140.

The comparator 138 compares the Wheatstone bridge voltage level outputwith a minimum reference value and generates a high output signal whenthe input level is below the minimum reference value V_(R min). Thecomparator 140 receives the bridge output signal and compares the signalvoltage level with a maximum reference level V_(R max). If the bridgeoutput voltage level is above the maximum reference value, thecomparator 140 generates a high output signal. The outputs of thecomparators 138, 140 are received at an amplifier and the amplifieroutput actuates the annunciator 116.

Further, the stabilization system is not limited to applications withload handling equipment, for example, the system may be utilized in avehicle subject to lateral tip over during operation, e.g. a sportsutility vehicle. In such instances, transducers are utilized as weightsensors in connection with one or more vehicle wheels to sense anapproaching condition wherein the wheel is about to be lifted from aroadway or other terrain which the vehicle is traversing. The transduceroutput is employed for annunciator actuation, for example, as depictedin FIG. 9 or, in a processor implementation, to actuate stabilizingcontrol responses, e.g. reduce vehicle speed, apply vehicle brakes.

Thus it will be seen that there is provided a stabilization system whichachieves the various aspects, features and considerations of the presentinvention and which is well suited to meet the conditions of practicalusage.

As various changes might be made in the present invention withoutdeparting from the spirit thereof, it is to be understood that allmatter herein described or shown in the accompanying drawings is to beinterpreted as illustrative and not in a limiting sense. For example,the load cell transducer need not be positioned about a steer wheelspindle but may be placed at any strategic location to measure theweight load on a support member. In a vehicle with a spring suspension,the cell may be attached to a suspension member such as a leaf spring,coil spring or torsion bar.

Further, load cell transducers need not be employed in all applications.Suitable fluidic or even optical transducers may be utilized. Invehicles with fluidic shock absorbers, for example, a fluid pressuretransducer may be employed.

Having thus described the invention, there is claimed as new and desiredto be secured by Letters Patent:
 1. A system for sensing the axialweight load carried by a support, the support including a substantiallyvertical member received in a socket, the vertical member having alongitudinal axis, the vertical member including an enlarged portionadjacent a lower end thereof, the enlarged portion terminating at anupper shoulder, the socket including a reduced diameter portionextending upwardly from a lower shoulder, an annular transducer, thetransducer having a diameter greater than the reduced diameter portionof the socket, the transducer being positioned along the longitudinalaxis between the lower shoulder of the socket and the upper shoulder ofthe vertical member, the transducer being subject to the axial weightload transferred between the reduced diameter portion of the socket andthe upper shoulder of the vertical member and the transducer generatinga signal in response to said axial weight load.
 2. A system for sensingthe weight load carried by a support as constructed in accordance withclaim 1 further including a steer wheel, the steer wheel being mountedto the lower end of the vertical member, the system further including abearing positioned on the vertical member between the transducer and theupper shoulder.
 3. A system for sensing the weight load carried by asupport as constructed in accordance with claim 1 wherein the transducercomprises a load cell, the system further including processing meansoperatively interconnected to the load cell, the processing meansreceiving the signal.
 4. A system for sensing the axial weight loadcarried by a support as constructed in accordance with claim 1 whereinthe vertical member comprises a spindle.
 5. A system for sensing theaxial weight load carried by a support member as constructed inaccordance with claim 4 further including a bearing, the bearing beingaxially positioned between the transducer and the upper shoulder of thevertical member, whereby the axial weight load carried by the support istransmitted from the lower shoulder of the socket, through thetransducer and through the bearing to the upper shoulder of the verticalmember.
 6. A system for sensing the axial weight load carried by asupport as constructed in accordance with claim 1 further including aprocessor, the processor receiving the signal generated by thetransducer, the processor determining when the axial load weight carriedby the vertical member is within a predetermined range of load weights.7. A system for sensing the axial load weight carried by a support asconstructed in accordance with claim 4 further including a mechanicallinkage coupled to the spindle for rotating the spindle about alongitudinal axis.
 8. A system for sensing the axial load weight carriedby a support as constructed in accordance with claim 7 further includinga motor, the motor being coupled to the mechanical linkage.
 9. A systemfor sensing the axial load weight carried by a support as constructed inaccordance with claim 4 further including a wheel mounted to thevertical member for rotation about an axis transverse to thelongitudinal axis of the vertical member.
 10. A system for sensing theaxial load weight carried by a support as constructed in accordance withclaim 1, the socket further including a tube, an upper portion of thevertical member being received in the tube.
 11. A system for sensing theaxial load weight carried by a support as constructed in accordance withclaim 4, the socket further including a tube, an upper portion of thespindle being received in the tube, the spindle being journalled forrotation about the longitudinal axis by a bearing positioned at an upperend of the tube.
 12. A system for sensing the axial load weight carriedby a support as constructed in accordance with claim 11 including afurther bearing positioned on the spindle between the transducer and theupper shoulder.
 13. A system for sensing a weight load being applied toa support, a lower portion of the support including a socket, an annularload cell surrounding the socket, the support including a verticalmember, an upper portion of the vertical member extending into thesocket, a lower portion of the vertical member being in engagement witha supporting surface, the lower portion of the vertical member bearingthe load weight of the support, the annular load cell being positionedbetween the lower portion of the support and the lower portion of thevertical member, the weight load being transmitted from the lowerportion of the vertical member through the load cell and to the lowerportion of the support surrounding the socket.
 14. A system for sensingthe weight load of a support as constructed in accordance with claim 13further including an annular bearing, the vertical member extendingthrough a central aperture of the bearing, the bearing being axiallypositioned between the load cell and the lower portion of the verticalmember.
 15. A system for sensing the weight load of a support asconstructed in accordance with claim 13 wherein the support includes atube registered with the socket, the upper portion of the verticalmember extending into the tube.
 16. A system for sensing the weight loadof a support as constructed in accordance with claim 15 including afurther bearing in engagement with the upper portion of the verticalmember and an upper end of the tube, the bearing and the further bearingbeing coaxial, the vertical member being journalled for rotation aboutthe common bearing axis.
 17. A method of sensing the axial load of aload carrier support, the load carrier including an annular socket in alower surface thereof and the support including a vertical member havingan upper portion the vertical member having an enlarged portion adjacenta lower end thereof, the method comprising the steps of: a) positioningan annular load cell in engagement with the socket, b) extending theupper portion of the vertical member through a bearing and through theload cell and into the socket, c) positioning the bearing between theenlarged portion of the vertical member and the load cell, d) engagingthe axial load of the carrier from the socket and through the load cellto the bearing and from the bearing to the enlarged portion of thevertical member, and e) processing axial load signals generated by theload cell.
 18. A method of sensing the axial weight load of a loadcarrier support in accordance with claim 17 including the further stepsof: f) providing a further bearing at an upper end of the socket withboth bearings being coaxial, and g) extending the upper portion of thevertical member through the further bearing, whereby the vertical membercan be rotated about the common axis of the bearings.